Clinical detection of 'cold stress' is overlooked: an online survey of healthcare workers to explore the gap in neonatal thermal care in low-resource settings.

BACKGROUND: Neonatal hypothermia has been widely regarded as a major contributory factor to neonatal mortality and morbidity in low-resource settings. The high prevalence of potentially preventable hypothermia today urges an investigation into why neonates still become hypothermic despite awareness of the problem and established thermal care guidelines. This study aimed to explore the gaps in knowledge and practices of neonatal thermal care among healthcare workers in low-resource settings. METHODS: A cross-sectional, questionnaire-based survey was performed online among healthcare workers in low-resource settings. We applied a purposive and snowballing sampling method to recruit participants through a two-round international online survey. Questionnaires were developed using themes of neonatal thermal care extracted from existing neonatal care guidelines. RESULTS: 55 neonatal care professionals participated in the first-round survey and 33 in the second. Almost all participants (n=44-54/55) acknowledged the importance of the WHO's warm chain to keep a neonate warm. However, fewer participants (n=34-46/55) responded to practice them. When asked about cold stress, defined as a condition in which neonates are below optimum environmental temperature and using more oxygen and energy while maintaining normal body temperature, 15 out of 55 participants answered that checking extremity temperatures by hand touch was useless. Some participants reported concern about the extremity temperature's inaccuracy compared with core temperature. Opinions and preferences for rewarming methods differed among participants, and so did the availability of warming equipment at their institutions. CONCLUSION: An inadequate understanding of cold stress underestimates the potential benefits of extremity temperatures and leads to missed opportunities for the timely prevention of hypothermia. The current thermal care guidelines fail to highlight the importance of monitoring cold stress and intervening before hypothermia occurs. Therefore, we urge introducing the concept of cold stress in any neonatal thermal care guidelines.

Translocon component Sec62 acts in endoplasmic reticulum turnover during stress recovery.

The endoplasmic reticulum (ER) is a site of protein biogenesis in eukaryotic cells. Perturbing ER homeostasis activates stress programs collectively called the unfolded protein response (UPR). The UPR enhances production of ER-resident chaperones and enzymes to reduce the burden of misfolded proteins. On resolution of ER stress, ill-defined, selective autophagic programs remove excess ER components. Here we identify Sec62, a constituent of the translocon complex regulating protein import in the mammalian ER, as an ER-resident autophagy receptor. Sec62 intervenes during recovery from ER stress to selectively deliver ER components to the autolysosomal system for clearance in a series of events that we name recovER-phagy. Sec62 contains a conserved LC3-interacting region in the C-terminal cytosolic domain that is required for its function in recovER-phagy, but is dispensable for its function in the protein translocation machinery. Our results identify Sec62 as a critical molecular component in maintenance and recovery of ER homeostasis.

Five Questions (with their Answers) on ER-Associated Degradation.

Production of a functional proteome is a major burden for our cells. Native proteins operate inside and outside the cells to eventually warrant life and adaptation to metabolic and environmental changes, there is no doubt that production and inappropriate handling of misfolded proteins may cause severe disease states. This review focuses on protein destruction, which is, paradoxically, a crucial event for cell and organism survival. It regulates the physiological turnover of proteins and the clearance of faulty biosynthetic products. It mainly relies on the intervention of two catabolic machineries, the ubiquitin proteasome system and the (auto)lysosomal system. Here, we have selected five questions dealing with how, why and when proteins produced in the mammalian endoplasmic reticulum are eventually selected for destruction.

Division of labor among oxidoreductases: TMX1 preferentially acts on transmembrane polypeptides.

The endoplasmic reticulum (ER) is the site of maturation for secretory and membrane proteins in eukaryotic cells. The lumen of the mammalian ER contains >20 members of the protein disulfide isomerase (PDI) superfamily, which ensure formation of the correct set of intramolecular and intermolecular disulfide bonds as crucial, rate-limiting reactions of the protein folding process. Components of the PDI superfamily may also facilitate dislocation of misfolded polypeptides across the ER membrane for ER-associated degradation (ERAD). The reasons for the high redundancy of PDI family members and the substrate features required for preferential engagement of one or the other are poorly understood. Here we show that TMX1, one of the few transmembrane members of the family, forms functional complexes with the ER lectin calnexin and preferentially intervenes during maturation of cysteine-containing, membrane-associated proteins while ignoring the same cysteine-containing ectodomains if not anchored at the ER membrane. As such, TMX1 is the first example of a topology-specific client protein redox catalyst in living cells.

N-linked sugar-regulated protein folding and quality control in the ER.

Asparagine-linked glycans (N-glycans) are displayed on the majority of proteins synthesized in the endoplasmic reticulum (ER). Removal of the outermost glucose residue recruits the lectin chaperone malectin possibly involved in a first triage of defective polypeptides. Removal of a second glucose promotes engagement of folding and quality control machineries built around the ER lectin chaperones calnexin (CNX) and calreticulin (CRT) and including oxidoreductases and peptidyl-prolyl isomerases. Deprivation of the last glucose residue dictates the release of N-glycosylated polypeptides from the lectin chaperones. Correctly folded proteins are authorized to leave the ER. Non-native polypeptides are recognized by the ER quality control key player UDP-glucose glycoprotein glucosyltransferase 1 (UGT1), re-glucosylated and re-addressed to the CNX/CRT chaperone binding cycle to provide additional opportunity for the protein to fold in the ER. Failure to attain the native structure determines the selection of the misfolded polypeptides for proteasome-mediated degradation.